1. Field of the Invention
The present invention relates to a fluid passage valve for switching a flow condition of a fluid by opening and closing a fluid passage through which the fluid flows.
2. Description of the Related Art
Heretofore, a fluid passage valve has been known, which is connected, for example, to a fluid passage through which a fluid flows, for controlling a flow condition of the fluid by switching a communication state of the fluid passage. In this type of fluid passage valve, a ball valve is provided in the interior of a valve main body, and by rotating a shaft, which is connected to an upper portion of the ball valve, a through hole of the ball valve causes a pair of passages (a gas fluid inlet and a gas fluid outlet) that are formed in the valve main body to be brought into communication with each other. Further, on the gas fluid inlet side and the gas fluid outlet side of the ball valve, a fixed seat and a movable seat are disposed sandwiching the ball valve therebetween, and the ball valve is retained between the fixed seat and the movable seat by means of a spring member, which urges the movable seat toward the side of the ball valve. As a result of this structure, because the ball valve is always maintained in contact with the fixed seat and the movable seat, the sealing characteristics thereof can be ensured (for example, refer to Japanese Laid-Open Patent Publication No. 57-114068).